Neptunium(VI) complexes with cyclopropane carbonic acid: unprecedented surrounding of neptunyl ion

The compounds (H3O)[NpO2(C4H5O2)3]3[NpO2(H2O)6] (1) and C(NH2)3[NpO2(C4H5O2)3] (2) were synthesized from aqueous solutions during isothermal evaporation at 20 deg C. Crystallographic data for compounds 1 and 2: space group R-3c, a = 15.620(2), c = 39.367(8) A, Z = 6, R = 0.040, wR(F2) = 0.102 (1), space group P21/n, a = 9.645(2), b 13.436(2), c = 14.277(2) A, β = 92.275(20), Z = 4, R = 0.034, wR(F2) 0.084 (2). The NIR and IR spectra of the compounds were also measured. The coordination polyhedrons of Np atoms in structures 1 and 2 are hexagonal bipyramids. There are two crystallographically unique Np atoms in the structure 1. The equatorial plane of the coordination polyhedron of the Np(1) atom is formed by oxygen atoms of anions of cyclopropane carbonic acid. The Np(1)-Oeq distances are 2.454(5)-2.482(5) A. The Np(1)O2 cation is nearly linear with the Np-O distances 1.737(5) A. The Np(2)O2 cation is linear, the Np-O distance are 1.70(1) A. The equatorial surrounding is formed by six water molecules with Np(2)-O distances 2.36(1) A. The surrounding of Np(2) atom formed by water molecules only has no precedent in transuranium elements compounds. The crystalline structure of 2 consists of C(NH2)3+ cations and complex anions [NpO2(C4H5O2)3]-. The Np-O distances of NpO2 cation are 1.744(5) and 1.752(5) A. The equatorial Np-O distances lie in the range from 2.437(5) to 2.497(5)